1. Field of the Invention
The present invention relates to a sensor which can detect an object such as a roll of paper held in a cassette and an ink-jet recording apparatus having it therein. Specifically the present invention relates to an ink-jet recording apparatus including: a sensor which is used in a maintenance mechanism in an ink-jet recording apparatus and is suitable for detecting a roll-like head cleaning paper held in a cassette; and the cassette.
2. Description of the Related Art
An ink-jet printer has a maintenance mechanism for cleaning the ink-jet head which ejects ink. For example, the maintenance mechanism in an ink-jet recording apparatus disclosed in Japanese Patent Application Laid-Open No.8-323,999, uses a roll of paper for cleaning. Upon maintenance, ink is forced to eject out from the ink-jet head toward the cleaning paper which has been pulled out from the roll of paper so that dust, air bubbles, etc. within the nozzle may be removed with the ink, and any ink on the nozzle surface is wiped by the cleaning paper. In this case, the paper is fed from the roll so that clean, unused cleaning paper opposes the ink-jet head. Thus, such a maintenance mechanism is used to clean the recording head so as to keep beneficial recording performance.
In the case where solid type ink (hot-melt ink) is used as in an ink-jet recording apparatus described in Japanese Patent Application Laid-Open No.8-323,999, if the cleaning paper is not closely abutted against the head, the head surface tends to be polluted because the ink ejected out from the nozzle solidifies instantly. Particularly, in a printer in which a cassette having a roll of paper therein was mounted to the printer body, if the cassette was not mounted correctly in place, the above problem would have occurred. If the printer was used with a used up roll of paper, the problem of the ejected ink polluting the maintenance mechanism and thereabout occurred because of the absence of the cleaning paper for receiving the ejected ink. Accordingly, in a printer where a cleaning cassette having a roll of paper therein is used, it was necessary to check whether the cassette was mounted correctly in place and whether there was an adequate amount of the roll of paper, for cleaning, left in the cassette.
While various types of sensors have been conventionally used in order to detect whether an object is present within a narrow space, a sensor for detecting the roll of paper accommodated in the cassette, for example, needs to operate in a considerably narrow space. Use of a mechanical sensor in which a movable arm or the like sways so as to turn on and off a limit switch, could prove inconvenient for such a limited space because of design requirements i.e., operational space is needed for on-off actions. Further, in the case of a sensor of this type, there is a limitation concerning the direction in which the object to be detected, or the target object, approaches the sensor. More specifically, there is a risk of the target object snagging the sensor due to the sensor configuration when it approaches the sensor in certain directions. Therefore, a sensor has been needed which can operate in a narrow space such as a cassette mounting area in an ink-jet printer and still is free from the snagging problem with the mounted object.
Conventional cassettes for maintenance are formed by molding individual parts with synthetic resins etc., and bonding the parts by heat welding etc. Therefore, it has been impossible to replace only the roll of paper alone, in the cassette, with a new one. Accordingly, despite the fact that the cassette is still usable, the whole cassette with a roll of paper must be discarded when it needs to be replaced. Therefore, the replacement of a roll of paper has imposed on the user a large burden in view of cost. Further, considering environmental problems and the problems of refuse which have been drawn to people's attention recently, it is not desirable to discard the reusable cassette casing together with the roll of paper.
A first object of the invention is to provide a detector for detecting an object such as a roll of paper etc., accommodated in a cassette, whereby it is possible to check whether the cassette is mounted correctly in place and whether the object is present in the cassette.
A second object of the invention is to provide a sensor which needs less operational space for a moving piece and has a configuration such that, regardless of its arrangement, the moving piece will not snag the target object approaching from any direction.
A third object of the invention is to provide an ink-jet recording apparatus having a maintenance mechanism therefor, including: a cassette in which a roll of paper for head cleaning is accommodated; and a detector suitable for detecting the roll of paper.